Naked DNA vaccines have shown promise for developing protective immunity by either T helper (Th)1 cell or Th2 cell-dependent responses. However, delivery has been primarily limited to peripheral sites rather than mucosal tissues. Consequently, minimal secretory (s)-IgA responses or immune mucosal Th cells are manifested. To successfully immunize the mucosa, efforts must consider the natural barriers at mucosal surfaces, and effectively target mucosal inductive tissues. In an effort to facilitate optimal mucosal immunity in the oral cavity, studies are proposed to utilize a DNA delivery system whereby the expression plasmid is complexed with a M cell-targeting molecule to ferry the DNA to mucosal inductive tissues following intranasal (i.n.) immunization. Much like live vector vaccine delivery systems which mediate host entry via M cells, it is hypothesized that the M cell ligand, reovirus protein sigma 1, will direct the DNA to the nasal-associated lymphoid tissue (NALT) and shared lymph nodes of the salivary-associated lymphoid tissues (SALT) for the appropriate stimulation of mucosal B and T cell subsets. Thus, the objective for this proposal is to test the effectiveness of this novel vaccine delivery system in promoting salivary s-IgA and IgG antibody responses. To further this effort, studies in Specific Aim 1 are focused in assessing the types and magnitude of mucosal antibody responses and the supportive CD4+ T cells induced following i.n. immunization with the protein sigma 1-directed DNA vaccine. Studies in Specific Aim 2 are focused on optimizing CTL responses by the SALT. For Specific Aim 3, to circumvent the possibility of inducing neutralizing antibodies against protein sigma 1, the M cell lectin from Ulex europaeus, will be tested for its ability to ferry the DNA vaccine to mucosal inductive tissues to elicit antigen-specific salivary antibody responses as well as their supportive CD4+ T cells. The last set of studies to be conducted will assess whether the incorporation of GM-CSF or IL-18 cDNA to co-immunize mice with the vaccine cDNA will improve mucosal IgA responses and mucosal CTL responses. These studies will provide the basis for future development of subunit vaccines to target the NALT for eliciting protective immunity in the oral cavity and SALT.